WO2016092043A1

WO2016092043A1 - Locking mechanism

Info

Publication number: WO2016092043A1
Application number: PCT/EP2015/079312
Authority: WO
Inventors: Julian Davis; Michael WILLETTS; Steven CRITCHARD; Andrew Cheeseman; Martin Stokes
Original assignee: Ge Oil & Gas Uk Limited
Priority date: 2014-12-12
Filing date: 2015-12-10
Publication date: 2016-06-16
Also published as: GB2533150A

Abstract

A method of locking a subsea electronics module 2 to a pressure isolation vessel3, said subsea electronics module comprising at least one cammed surface 4 on an outer surface thereof and said pressure isolation vessel comprising at least one cammed surface on an inner surface thereof, the method comprising the steps of: inserting the subsea electronics module into the pressure isolation vessel; and rotating the subsea electronics module in a first direction to cause at least one cammed surface of the subsea electronics module to engage with at least one corresponding cammed surface of the pressure isolation vessel to form an interference fit between the subsea electronics module and the pressure isolation vessel.

Description

LOCKING MECHANISM

This invention relates to a method of locking a subsea electronics module (SEM) to a pressure isolation vessel. The invention also relates to a SEM and a pressure isolation vessel for use in such a method, and an assembly comprising the SEM and pressure isolation vessel.

Background

A subsea electronics module (SEM) is a common component of underwater hydrocarbon extraction facilities. Typically, a SEM comprises a generally cylindrical body containing a plurality of circuit boards, e.g. single board computer (SBC) cards, arranged in a stack on a motherboard. The generally cylindrical body has a tail-stock and a front end assembly at one end, and a ported endcap assembly at the other. Often, the tail-stock is bolted to the front end assembly. The portion between the tail- stock and the ported endcap assembly forms the chassis of the SEM. The SBCs contain control circuitry for operating a subsea control module (SCM) which controls the operations of a subsea well.

As SEMs are located on the sea bed in use, they must be able to withstand high external pressures. To this end, they are usually contained within pressure isolation vessels. In the prior art, the effective restraint of the SEM within the pressure isolation vessel has relied upon a precision fit mandrel or spigot-based interface that has been achieved either through machining or via custom potting (wet assembly of the SEM and pressure isolation vessel). Spring-loaded thermal interface blocks have previously been used to provide alternative heat export paths from the SEM chassis spine rails to the vessel but these do not provide secure mechanical registration of the SEM within the pressure isolation vessel.

A prior art apparatus for clamping circuit cards within a case is disclosed in US7269895. A prior art apparatus for improving heat export between a printed circuit board and a chassis is disclosed in US8223497. The present invention is directed towards a locking mechanism for a SEM and a pressure isolation vessel that attempts to overcome some of the drawbacks associated with prior art locking mechanisms.

Summary of the invention

In accordance with a first aspect of the present invention there is provided a subsea electronics module having at least one cammed surface on an outer surface thereof.

In accordance with a second aspect of the present invention there is provided a pressure isolation vessel having at least one cammed surface on an inner surface thereof.

In accordance with a third aspect of the present invention there is provided an assembly comprising such a subsea electronics module and such a pressure isolation vessel, wherein the subsea electronics module is insertable into the pressure isolation vessel, and rotation of the subsea electronics module in a first direction when inserted into the pressure isolation vessel causes at least one cammed surface of the subsea electronics module to engage with at least one corresponding cammed surface of the pressure isolation vessel to form an interference fit between the subsea electronics module and the pressure isolation vessel.

In accordance with a fourth aspect of the present invention there is provided a method of locking a subsea electronics module to a pressure isolation vessel, said subsea electronics module comprising at least one cammed surface on an outer surface thereof and said pressure isolation vessel comprising at least one cammed surface on an inner surface thereof, the method comprising the steps of: inserting the subsea electronics module into the pressure isolation vessel; and rotating the subsea electronics module in a first direction to cause at least one cammed surface of the subsea electronics module to engage with at least one corresponding cammed surface of the pressure isolation vessel to form an interference fit between the subsea electronics module and the pressure isolation vessel.

The at least one cammed surface may extend from a tailstock of the subsea electronics module.

The at least one cammed surface may extend from a front end assembly of the subsea electronics module.

The at least one cammed surface may extend from a spine rail adaptor of the subsea electronics module.

The at least one cammed surface may extend from an Ethernet switch blade carrier ladder of the subsea electronics module.

The at least one cammed surface may extend from a cover plate of the subsea electronics module.

The subsea electronics module may have at least two cammed surfaces that extend from diametrically opposite sides of the subsea electronics module. In this case, the subsea electronics module could have two further cammed surfaces that extend from diametrically opposite sides of the subsea electronics module.

The subsea electronics module could have a plurality of cammed surfaces equally spaced around a circumference of the subsea electronics module.

The pressure isolation vessel could have at least two cammed surfaces that extend diametrically opposite each other. In this case, the pressure isolation vessel could have two further cammed surfaces that extend diametrically opposite each other.

The pressure isolation vessel could have a plurality of cammed surfaces equally spaced around an inner circumference of the pressure isolation vessel.

The at least one cammed surface could form a thermal bridge between the subsea electronics module and the pressure isolation vessel when engaged with a corresponding cammed surface of the pressure isolation vessel. Rotation of the subsea electronics module in a second direction opposite to the first direction could cause at least one cammed surface of the subsea electronics module to disengage with a corresponding cammed surface of the pressure isolation vessel.

Detailed Description

The invention will now be described by way of example with reference to the accompanying drawings, in which:

Fig. 1 schematically shows a cross-sectional view of a locking mechanism according to a first embodiment of the invention;

Fig. 2 schematically shows a cross-sectional view of the locking mechanism of Fig. 1 in a locked position;

Fig. 3 schematically shows a cross-sectional view of a locking mechanism according to a second embodiment of the invention;

Fig. 4 schematically shows a cross-sectional view of the locking mechanism of Fig. 3 in a locked position; and

Fig. 5 schematically shows a cross-sectional view of a locking mechanism according to a third embodiment of the invention.

Fig. 1 schematically shows a locking mechanism 1. The locking mechanism 1 is shown in a disengaged or open position.

A subsea electronics module (SEM) 2 has been inserted into a pressure isolation vessel 3. Both the SEM 2 and pressure isolation vessel 3 are generally cylindrical in shape, with the pressure isolation vessel 3 being of greater diameter than the SEM 2 such that the SEM 2 can fit inside it. The cross-sectional view of Fig. 1 is taken at one end of the SEM 2, in the region of its tailstock.

A tailstock of the SEM 2 has four cammed surfaces spaced at equal distances around its circumference. One of the cammed surfaces is indicated at reference numeral 4. In this embodiment, the cammed surfaces are mounted on the tailstock of the SEM 2 and extend outwardly therefrom. However, in other embodiments the cammed surfaces may be integrally formed with the tailstock during its manufacture.

The pressure isolation vessel has four corresponding cammed surfaces mounted at equal distances around its internal wall. One of the cammed surfaces is indicated at reference numeral 5.

In order to lock the SEM 2 within the pressure isolation vessel 3, the SEM 2 is rotated in a first, clockwise direction from the position shown in Fig. 1. Each of the cammed surfaces of the SEM 2 engage with a respective one of the cammed surfaces of the pressure isolation vessel 3. The cammed surfaces of the SEM 2 deform to comply with the cammed surfaces of the pressure isolation vessel on rotation, resulting in an interference fit.

Fig. 2 schematically shows the locking mechanism 1 of Fig. 1 in a locked position. Like reference numerals have been retained as appropriate.

The cammed surfaces of the SEM 2 are engaged with the corresponding cammed surfaces over a large surface area compared to prior art locking mechanisms, and consequently this gives both improved mechanical and thermal engagement between the SEM 2 and the pressure isolation vessel 3. This is desirable, as there is a requirement to export heat from the SEM 2 in use. This locking mechanism 1 provides a new thermal path which enables the conduction of heat from the SEM 2 to the pressure isolation vessel 3, from which heat can be exported to the surrounding environment.

While Figs. 1 and 2 have been described with the locking mechanism 1 applied to a tailstock of the SEM 2, it could equally be applied to a front end assembly (FEA) of the SEM 2, or to a ported endcap assembly (PEA) of the SEM 2.

Fig. 3 schematically shows a locking mechanism 6. It shows the same SEM 2 and pressure isolation vessel 3 of Figs. 1 and 2, however the cross-section is taken from a point in the centre of the SEM 2 rather than at one end. Like reference numerals have been retained where appropriate. This central region of the SEM 2 comprises a card frame 7. The card frame 7 holds a plurality of circuit boards arranged in a parallel stack and connected to each other via a motherboard 8. The motherboard 8 is covered by a wedge profiled cover plate 9 which encloses a wiring void 10. The cover plate 9 has a cammed surface which corresponds to a cammed surface 11 mounted on an internal surface of the pressure isolation vessel 3.

An upper surface (as shown in Fig. 3) of the card frame 7 has a spine rail adaptor 12. A SEM chassis spine rail cammed surface 13 is located on the spine rail adaptor 12. The SEM chassis spine rail cammed surface 13 corresponds to a cammed surface 14 mounted on an internal surface of the pressure isolation vessel 3. This arrangement is replicated on the lower surface of the card frame 7, where a spine rail adaptor 15 has a SEM chassis spine rail cammed surface 16 located thereon. The SEM chassis spine rail cammed surface 16 corresponds to a cammed surface 17 mounted on an internal surface of the pressure isolation vessel 3.

An Ethernet switch blade (ESB) 18, i.e. a communication handling board, is located on one side of the card frame 7, perpendicular to the stack of circuit boards. An ESB carrier ladder 19 is disposed over the ESB 18, and a SEM chassis cammed surface 20 is mounted thereon. The SEM chassis cammed surface 20 corresponds to a cammed surface 21 mounted on an internal surface of the pressure isolation vessel 3. A cover plate 22 is located between the ESB carrier ladder 19 and the card frame 7, however unlike the cover plate 9 on the opposite side of the card frame 7, this cover plate 22 is not adapted to engage with a cammed surface on the pressure isolation vessel 3.

Fig. 4 schematically shows a cross-sectional view of the locking mechanism of Fig. 3 in a locked position. The SEM 2 has been rotated in a clockwise direction from the position shown in Fig. 3. The diametrically opposed SEM chassis spine rail cammed surfaces 13 and 16 have engaged with respective corresponding cammed surfaces 14 and 17 mounted on an internal surface of the pressure isolation vessel 25. The cover plate 9 has engaged with a respective corresponding cammed surface 11 mounted on an internal surface of the pressure isolation vessel 3. The ESB SEM chassis cammed surface 20 has engaged with the corresponding cammed surface 21 mounted on an internal surface of the pressure isolation vessel.

Fig. 5 schematically shows a cross-sectional view of a locking mechanism 23 according to a third embodiment of the invention. The locking mechanism 23 comprises a SEM 24 which has been inserted into a pressure isolation vessel 25. The cross-section of Fig. 5 is taken in the region of a tailstock of the SEM 24.

The SEM 24 has three cammed surfaces extending from its outer surface. One cammed surface is indicated at reference numeral 26. The three cammed surfaces are equally spaced around a circumference of the SEM 24.

The pressure isolation vessel 25 has three cammed surfaces extending from its inner surface. One cammed surface is indicated at reference numeral 27. The three cammed surfaces are equally spaced around the interior surface of the pressure isolation vessel 25, and each cammed surface corresponds to a respective cammed surface of the SEM 24.

In the examples shown in Figs. 1, 3 and 5, rotation of the SEM 2 or 24 in a first (clockwise) direction by around 30 degrees engages the cammed surfaces of the SEM 2 or 24 with respective cammed surfaces on the pressure isolation vessel 3 or 25. Rotation of the SEM 2 or 24 in a second (anti-clockwise) opposite direction by around 30 degrees disengages the cammed surfaces of the SEM 2 or 24 with the respective cammed surfaces of the pressure isolation vessel 3 or 25. The angle of rotation required can be increased or decreased as desired for each specific application, for example by increasing the depth or angle of the cammed surface of the SEM 2 or 24 or the pressure isolation vessel 3 or 25. The SEM 2 or 24 can be readily rotated within the pressure isolation vessel 3 or 25 after full insertion by using a torsion bar (tommy bar) connected to a suitable adaptor fitted in place of a SEM lifting adaptor.

The cammed surfaces of the SEM can be formed from, or clad/lined with, soft metal (for example, copper, lead, solder or aluminium) designed to distort/compress as the SEM is rotated into place 'taking up' any physical gaps (voids) between the cammed surfaces of the SEM 2 or 24 and the cammed surfaces of the pressure isolation vessel 3 or 25. The filling in of these physical gaps results in improved heat export, as the engaged cammed surfaces form an effective thermal bridge.

Where the cammed surface is a cover plate 9 of the SEM 2, this can be formed of a less compliant and more elastic material than that employed to fabricate spine rail cams. The spine rail cammed surfaces are preferably designed to be readily and cheaply replaceable after use.

The cammed surfaces of the pressure isolation vessel can also be formed from, or clad/lined with, soft metal (for example, copper, lead, solder or aluminium) or from a honeycomb facing material (for example, carbon or copper) or from any suitable conventional thermal gasket material.

The materials of the cammed surfaces of the SEM and the pressure isolation vessel are preferably compliant with one another to maximise the metal to metal contact area and thereby optimise the heat export from the electrical components of the SEM to the pressure isolation vessel side walls.

Forming the cammed surfaces of the SEM and the pressure isolation vessel of soft metal is preferable, as it gives a larger degree of manufacturing tolerance. As the cammed surfaces of the SEM and the pressure isolation vessel will deform to a relatively large degree, they do not need to be as precisely machined as components which deform to a lesser degree.

Advantages of the invention

There are numerous advantages associated with the present invention. For example, it enables improved mechanical and thermal engagement between a SEM and a pressure isolation vessel. The larger surface area provided by the locking mechanism of the present invention (when compared with prior art locking mechanisms) provides an enhanced thermal bridge between a SEM and a pressure isolation vessel, which improves heat export from the electrical components of the SEM.

The present invention enables the maximum (optimum) use of the pressure isolation vessel internal surface area to both mechanically support the SEM and to provide a heat export path for internally generated heat. Prior art SEM designs are only mechanically registered by a ported end-cap and a blind end-cap tail stock, the main body of the SEM being supported as a beam assembly. The present invention may, in the limit, provide cammed surfaces over the entire length of the SEM. This enables the SEM to be mechanically supported in the pressure isolation vessel over its entire length, thereby enhancing the overall mechanical integrity of the whole assembly.

The present invention enables the SEM to be pressed into contact with the pressure isolation vessel with significantly more force (pressure) than could be achieved with a sprung interface that could be practicably inserted into the pressure isolation vessel. Thermal and mechanical interface contact force can therefore be maximised without requiring the application of significant force during the insertion of the SEM into the pressure isolation vessel. A low insertion force for the insertion of the SEM into the pressure isolation vessel is particularly important when finally engaging the ported end-cap to vessel seals (i.e. the final stage of the insertion) where it is desirable to be able to 'feel' the seal engagement. This is not practicable if the insertion force required to achieve chassis insertion is dominated by the interference fit of the SEM sprung thermal interface with the pressure isolation vessel.

Metal to metal contact areas of cammed surfaces can be designed to be significantly greater than those achievable with sprung interfaces and will have no obvious air voids, as these are eliminated as the cammed surfaces bear against one another on rotation. As a consequence the thermal impedance through the cammed interfaces for heat export will be lower than for a similarly sized sprung interface.

The tapered sides of the cammed surfaces of the SEM and the pressure isolation vessel gives a degree of clearance between the SEM and the wall of the pressure isolation vessel. This enables the SEM to be easily inserted into the pressure isolation vessel without the need to compress sprung interfaces or overcome an interference fit against a wall of the pressure isolation vessel that would otherwise impede the insertion of the SEM into the pressure isolation vessel, thereby avoiding SEM and, in particular, seal damage in the process. The tapered sides serve a dual purpose of allowing this clearance during insertion, yet still providing a tight interference fit following rotation.

The present invention accommodates the accumulation of SEM and pressure isolation vessel mechanical tolerances resulting from piece part manufacture and general assembly. This enables a secure and precise mechanical registration of the SEM to the pressure isolation vessel to be achieved without requiring high levels of precision for piece part machining and assembly. It also avoids the need for wet assembly (potted assembly) techniques currently utilised to mechanically and thermally register the SEM tail-stock to the base of the pressure isolation vessel. Such techniques can require numerous COSHH (control of substances hazardous to health) processes which are both time consuming and involve the use of potentially hazardous chemicals.

Sacrificial compliant cams or cam facing material can be readily fitted and replaced thereby augmenting the manufacturability and serviceability of the SEM in comparison with the wet assembly techniques currently employed for SEM manufacture.

The invention is not limited to the specific embodiments disclosed above, and other possibilities will be apparent to those skilled in the art. For example, the examples shown in Figs. 1 to 4 use four cammed surfaces on the SEM and four cammed surfaces on the pressure isolation vessel. This arrangement is preferable, as using two pairs of diametrically opposed cammed surfaces centres the SEM within the pressure isolation vessel. This centring effect is also achieved using a design with three cammed surfaces, such as that shown in Fig. 5. Using only a single cammed surface does not provide this centring effect, and is therefore less useful, though still within the scope of the present invention.

A pair of diametrically opposed cammed surfaces may be particularly suitable for use on the chassis of the SEM, as the cross-section of the SEM at this point may be rectangular. Three cammed surfaces may be more suitable for use on the tail-stock or front end assembly of the SEM, as the cross-section of the SEM at this point may be generally circular. However, all combinations of cammed surfaces at all points along the SEM fall within the scope of the present invention.

The cammed surfaces can take any graduated form, such as a straight diagonal gradient or a curve. The SEM outer surface may be generally ovate in shape. Alternatively, the outer surface of the SEM could have the shape of a snail cam.

Generally, more cammed surfaces are preferable as they provide more points of support for the SEM inside the pressure isolation vessel, which increases the ruggedness of the SEM. However, any number of cammed surfaces could be used in practice (a single cammed surface on the SEM and a single corresponding cammed surface on the pressure isolation vessel being the minimum possible).

Additionally, the examples shown in Figs. 1-5 have the cammed surfaces of the SEM and the pressure isolation vessel arranged at equal spacings around the circumference of the SEM and pressure isolation vessel. This is also not a requirement in practice, and cammed surfaces of the SEM or pressure isolation vessel could be closer to, or further from, each other provided that each cammed surface of the SEM has a corresponding cammed surface on the pressure isolation vessel. However, the four cammed surfaces on the SEM and the pressure isolation vessel arrangement shown in Figs. 1 to 4 is particularly advantageous in that it prevents the SEM from moving in any direction in the pressure isolation vessel following rotation.

It is within the scope of the present invention for the SEM to have a cammed surface on the tailstock only, on the front end assembly only, on the ported endcap assembly only, or only on its central portion on the spine rail adaptor, Ethernet switch blade carrier ladder or cover plate. It is also within the scope of the present invention for the SEM to have cammed surfaces on any combination of these. For example, a SEM with cammed surfaces on the tailstock and the front end assembly, a SEM with cammed surfaces on the tailstock and a spine rail adaptor, a SEM with cammed surfaces on the tailstock and an Ethernet switch blade carrier ladder, a SEM with cammed surfaces on the tailstock and a cover plate, a SEM with cammed surfaces on the front end assembly and a spine rail adaptor, a SEM with cammed surfaces on the front end assembly and an Ethernet switch blade carrier ladder, a SEM with cammed surfaces on the front end assembly and a cover plate, or a SEM with cammed surfaces on the tailstock, front end assembly, spine rail adaptor, Ethernet switch blade carrier ladder and cover plate.

Claims

CLAIMS:

1. A subsea electronics module having at least one cammed surface on an outer surface thereof.

2. A subsea electronics module according to claim 1, wherein the at least one cammed surface extends from a tailstock of the subsea electronics module.

3. A subsea electronics module according to claim 1, wherein the at least one cammed surface extends from a front end assembly of the subsea electronics module.

4. A subsea electronics module according to any of claims 1 to 3, wherein the at least one cammed surface extends from a spine rail adaptor of the subsea electronics module.

5. A subsea electronics module according to any preceding claim, wherein the at least one cammed surface extends from an Ethernet switch blade carrier ladder of the subsea electronics module.

6. A subsea electronics module according to any preceding claim, wherein the at least one cammed surface extends from a cover plate of the subsea electronics module.

7. A subsea electronics module according to any preceding claim, comprising at least two cammed surfaces that extend from diametrically opposite sides of the subsea electronics module.

8. A subsea electronics module according to claim 7, wherein the subsea electronics module has two further cammed surfaces that extend from diametrically opposite sides of the subsea electronics module.

9. A subsea electronics module according to any preceding claim, wherein the subsea electronics module has a plurality of cammed surfaces equally spaced around a circumference of the subsea electronics module.

10. A pressure isolation vessel having at least one cammed surface on an inner surface thereof.

11. A pressure isolation vessel according to claim 10, wherein the pressure isolation vessel has at least two cammed surfaces that extend diametrically opposite each other.

12. A pressure isolation vessel according to claim 11, wherein the pressure isolation vessel has two further cammed surfaces that extend diametrically opposite each other.

13. A pressure isolation vessel according to any of claims 9 to 11, wherein the pressure isolation vessel has a plurality of cammed surfaces equally spaced around an inner circumference of the pressure isolation vessel.

14. An assembly comprising a subsea electronics module according to any of claims 1 to 9 and a pressure isolation vessel according to any of claims 10 to 13, wherein the subsea electronics module is insertable into the pressure isolation vessel, and rotation of the subsea electronics module in a first direction when inserted into the pressure isolation vessel causes at least one cammed surface of the subsea electronics module to engage with at least one corresponding cammed surface of the pressure isolation vessel to form an interference fit between the subsea electronics module and the pressure isolation vessel.

15. An assembly according to claim 14, wherein rotation of the subsea electronics module in a second direction opposite to the first direction will cause at least one cammed surface of the subsea electronics module to disengage with a corresponding cammed surface of the pressure isolation vessel.

16. An assembly according to claim 14 or 15, wherein at least one cammed surface of the subsea electronics module forms a thermal bridge between the subsea electronics module and the pressure isolation vessel when engaged with a corresponding cammed surface of the pressure isolation vessel.

17. A method of locking a subsea electronics module to a pressure isolation vessel, said subsea electronics module comprising at least one cammed surface on an outer surface thereof and said pressure isolation vessel comprising at least one cammed surface on an inner surface thereof, the method comprising the steps of: inserting the subsea electronics module into the pressure isolation vessel; and rotating the subsea electronics module in a first direction to cause at least one cammed surface of the subsea electronics module to engage with at least one corresponding cammed surface of the pressure isolation vessel to form an interference fit between the subsea electronics module and the pressure isolation vessel.

18. A method according to claim 17, wherein the at least one cammed surface extends from a tailstock of the subsea electronics module.

19. A method according to either of claims 17 and 18, wherein the at least one cammed surface extends from a front end assembly of the subsea electronics module.

20. A method according to any of claims 17 to 19, wherein the at least one cammed surface extends from a spine rail adaptor of the subsea electronics module.

21. A method according to any of claims 17 to 20, wherein the at least one cammed surface extends from an Ethernet switch blade carrier ladder of the subsea electronics module.

22. A method according to any of claims 17 to 21, wherein the at least one cammed surface extends from a cover plate of the subsea electronics module.

23. A method according to any of claims 17 to 22, wherein at least two cammed surfaces extend from diametrically opposite sides of the subsea electronics module.

24. A method according to claim 23, wherein the subsea electronics module has two further cammed surfaces that extend from diametrically opposite sides of the subsea electronics module.

25. A method according to any of claims 17 to 24, wherein the subsea electronics module has a plurality of cammed surfaces equally spaced around a circumference of the subsea electronics module.

26. A method according to any of claims 17 to 25, wherein the pressure isolation vessel has at least two cammed surfaces that extend diametrically opposite each other.

27. A method according to claim 26, wherein the pressure isolation vessel has two further cammed surfaces that extend diametrically opposite each other.

28. A method according to any of claims 17 to 27, wherein the pressure isolation vessel has a plurality of cammed surfaces equally spaced around an inner circumference of the pressure isolation vessel.

29. A method according to any of claims 17 to 28, wherein at least one cammed surface of the subsea electronics module forms a thermal bridge between the subsea electronics module and the pressure isolation vessel when engaged with a corresponding cammed surface of the pressure isolation vessel.

30. A method according to any of claims 17 to 29, wherein rotation of the subsea electronics module in a second direction opposite to the first direction will cause at least one cammed surface of the subsea electronics module to disengage with a corresponding cammed surface of the pressure isolation vessel.

31. A subsea electronics module substantially as hereinbefore described with reference Figs. 1 to 5.

32. A pressure isolation vessel substantially as hereinbefore described with reference Figs. 1 to 5.

33. An assembly substantially as hereinbefore described with reference Figs. 1 to 5.

34. A method of locking a subsea electronics module to a pressure isolation vessel substantially as hereinbefore described with reference to Figs. 1 to 5.